fix: support semver ranges in tsp init template compilerVersion

.chronus/changes/fix-template-compiler-version-range-2026-7-30.md

@@ -0,0 +1,7 @@
+---
+changeKind: fix
+packages:
+  - "@typespec/compiler"
+---
+
+`tsp init` template `compilerVersion` field now supports semver ranges (e.g., `^0.50.0`). Plain versions like `1.2.3` continue to work as `>=1.2.3` for backward compatibility.

packages/compiler/src/init/init.ts

@@ -319,12 +319,18 @@ async function promptTemplateSelection(templates: Record<string, any>): Promise<
   return templateName;
 }
 
-function isTemplateCompatibleWithTspVersion(template: InitTemplate): boolean {
+/** @internal */
+export function isTemplateCompatibleWithTspVersion(template: InitTemplate): boolean {
   const currentCompilerVersion = MANIFEST.version;
-  return (
-    template.compilerVersion === undefined ||
-    semver.gte(currentCompilerVersion, template.compilerVersion)
-  );
+  if (template.compilerVersion === undefined) {
+    return true;
+  }
+  // If it's a plain version (e.g., "1.2.3"), treat it as >= for backward compatibility
+  if (semver.valid(template.compilerVersion)) {
+    return semver.gte(currentCompilerVersion, template.compilerVersion);
+  }
+  // Otherwise treat it as a semver range (e.g., "^1.2.3", ">=1.2.3")
+  return semver.satisfies(currentCompilerVersion, template.compilerVersion);
 }
 
 async function validateTemplate(template: any, index: LoadedTemplateIndex): Promise<boolean> {

packages/compiler/test/cli/init.test.ts

@@ -1,8 +1,13 @@
-import { afterAll, afterEach, beforeEach, expect, it, vi } from "vitest";
+import { afterAll, afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import { CliCompilerHost } from "../../src/core/cli/types.js";
 import { resolvePath } from "../../src/core/path-utils.js";
 import { LogSink } from "../../src/index.js";
-import { initTypeSpecProject, InitTypeSpecProjectOptions } from "../../src/init/init.js";
+import { InitTemplate } from "../../src/init/init-template.js";
+import {
+  initTypeSpecProject,
+  InitTypeSpecProjectOptions,
+  isTemplateCompatibleWithTspVersion,
+} from "../../src/init/init.js";
 import { UriTemplateSource } from "../../src/init/template-source/index.js";
 import { createTestFileSystem } from "../../src/testing/fs.js";
 import { TestFileSystem } from "../../src/testing/types.js";
@@ -308,3 +313,39 @@ it("should fallback to 'latest' when npm registry is unreachable", async () => {
   const packageJson = await parseJson(compilerHost, "/tmp/test-project/package.json");
   expect(packageJson.dependencies["@typespec/compiler"]).toBe("latest");
 });
+
+describe("isTemplateCompatibleWithTspVersion", () => {
+  function makeTemplate(compilerVersion: string | undefined): InitTemplate {
+    return {
+      title: "Test",
+      description: "Test template",
+      compilerVersion,
+    };
+  }
+
+  it("returns true when compilerVersion is undefined", () => {
+    expect(isTemplateCompatibleWithTspVersion(makeTemplate(undefined))).toBe(true);
+  });
+
+  it("returns true when plain version is less than or equal to current (backward compat: plain version means >=)", () => {
+    // Current version is 1.14.0; a plain version <= current should be compatible
+    expect(isTemplateCompatibleWithTspVersion(makeTemplate("0.44.0"))).toBe(true);
+    expect(isTemplateCompatibleWithTspVersion(makeTemplate("1.0.0"))).toBe(true);
+  });
+
+  it("returns false when plain version is greater than current", () => {
+    expect(isTemplateCompatibleWithTspVersion(makeTemplate("99.0.0"))).toBe(false);
+  });
+
+  it("returns true when semver range is satisfied by current version", () => {
+    expect(isTemplateCompatibleWithTspVersion(makeTemplate("^1.0.0"))).toBe(true);
+    expect(isTemplateCompatibleWithTspVersion(makeTemplate(">=1.0.0"))).toBe(true);
+    expect(isTemplateCompatibleWithTspVersion(makeTemplate("^1.14.0"))).toBe(true);
+  });
+
+  it("returns false when semver range is not satisfied by current version", () => {
+    expect(isTemplateCompatibleWithTspVersion(makeTemplate("^2.0.0"))).toBe(false);
+    expect(isTemplateCompatibleWithTspVersion(makeTemplate(">=99.0.0"))).toBe(false);
+    expect(isTemplateCompatibleWithTspVersion(makeTemplate("^0.50.0"))).toBe(false);
+  });
+});